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2. Al. Duca, C. Calu, and M. Bezdadea, Chimie Analitica (Bucharest)1, 169 (1971).
3. Al. Duca and M. Gaburici, unpublished work.
4. Gh. Ionescu and Al. Duca, unpublished work.
5. S. Goldstein, A. Ciupitoiu, V. Vasilescu, and Al. Duca, Mikrochim. Acta [Wien],1975 I, 129; Canad. J. Pharm. Sci.9, 116 (1974).